A. Field of Invention
The present invention relates to magnetic sensors, and more particularly, to shielding a magnetic sensing device from electromagnetic signals generated from within.
B. Description of Related Art
Magnetic sensors are typically used for direction finding or other means of navigation. The technology for sensing magnetic fields has evolved due to the need for improved sensitivity, smaller size, and compatibility with electronic systems.
Most navigation systems today use some type of magnetic compass to determine a heading direction. Using the Earth's magnetic field, electronic compasses based on magnetoresistive (MR) sensors can electrically resolve better than a 0.1 degree rotation of direction. An MR sensor measures the change in electrical resistance due to an external electrical or magnetic field. For example, the Earth's magnetic fields can cause a change in the resistance of an MR sensor, from which compass headings can be determined.
MR sensors provide a solid-state solution for building compass navigation systems. Their high sensitivity and effective repeatability, along with small size, results in a high accuracy magnetic sensor. However, integrating an MR sensor with electronic circuitry may not result in accurate magnetic measurements. Electromagnetic signals, such as current signals, within the electronic circuitry may interfere with signals from the Earth's magnetic field, and therefore, an accurate measurement of the Earth's magnetic field may not be obtained. An electric current always produces a magnetic field, which will interfere with a measurement of a low intensity magnetic field.
Existing MR sensor systems lack an ability to eliminate or reduce the magnetic field effects generated by electronics within the system, and so it is desirable to provide a device that eliminates stray electromagnetic signals in order to accurately measure a magnetic field.